i have a formula fas tech 353 with 500efi and zx drives spining 4 blades 30 labs . the boat has 160 hours on it and have never seen 80mph with yet best i ever got was 4850rpm at 77.7 mph gps any tell me why i ant turning at least 5 grand and what elese to to do get rpm and mph i have heard facing drives in ward gets you 1 to 2 mph get back to me .

Try a smaller prop. maybe a 28 four blade.

1 zx drives?

2 props need to spin in( well not "need" but will be faster)

3 check the props... 30 labbed doesnt mean 30 labbed, have the pitch checked also who labbed them? sounds like a botched job non labbed should be 80mph

4 where are you? altitude?fresh or salt?

The 353 has too much negative trim so straight edge the drives with the bottom and mark that on your indicator as neutral. Then trim it up 2-3 clicks from there. You may want to try some hydromotive 27 pitch 5 blades on that boat. You are not getting enough rpm!

my bad xz drives and i live in toms river Nj salt water .